aria-activedescendant mapping doesn't seem to be explicitly described in Core-AAM.

[alice]

http://w3c.github.io/core-aam/#statePropertyMappingGeneralRules says:

The FOCUSABLE/FOCUSED states may be affected by aria-activedescendant.

https://w3c.github.io/core-aam/#ariaActiveDescendant defers to the Focus Changes section, which doesn't mention aria-activedescendant at all.

Does the issue exist in the editors draft (the editors draft is the most recent draft of the specification)?

Yes.